The present invention relates to methods for repelling insects from a host and compositions effective for the same. More specifically, these compositions have superior stability with respect to degradation of the active material and are gentle to the skin.
There are many known insect repellant formulations that use a variety of insect repellant active materials. See, e.g., European patent applications 97,812 and 97,813, and U.S. Pat. Nos. 4,127,672, 4,756,905, 5,465,685, 5,489,433, 5,565,208, 5,672,337 and 5,716,602.
Many of the commercially available insect repellant formulations include insect repellant active materials which contain one or more ester, amide or urethane functionalities. Disadvantageously, these materials are hydrolytically sensitive and often degrade upon long term storage in contact with aqueous media.
Other commercially available insect repellant formulations that contain water insoluble active materials frequently contain a significant amount of solubilizers such as lower monohydric alcohols, i.e., ethanol and isopropanol. However, the amount of such lower alcohols present in these formulations often contributes to drying and irritation of the skin.
It would be desirable to provide a composition that exhibited a reduced rate of decomposition of the insect repellant active material without causing significant drying and irritation to the skin.
In accordance with the present invention, we have found an insect repellant composition comprising, consisting essentially of, or consisting of, based upon the total weight of the composition:
a. from about 6 to about 30 percent of insect repellant active material, said active material containing a functionality selected from ester, amide, urethane or combinations thereof;
b. from about 5 to about 30 percent of alcohol selected from
i. ethanol;
ii. isopropanol;
iii. a glycol monoalkyl ether, said alkyl having from about 1 carbon atom to about 4 carbon atoms;
iv. a glycol containing from about 3 carbon atoms to about 6 carbon atoms;
v. oligomers of ethylene glycol or propylene glycol; or
vi. mixtures thereof; and
c. from about 1 to about 10 percent by weight of surfactant.
In another embodiment of the present invention we have found a method of reducing the rate of degradation of an insect repellant active material in an aqueous composition, said active material containing functionality selected from ester, amide, urethane or combinations thereof, comprising, consisting of, or consisting essentially of incorporating into the composition under conditions sufficient a degradation-effective amount of a surfactant.
In yet another embodiment of the present invention we have found a method of repelling insects from a host comprising, consisting essentially of, or consisting of:
topically applying to the host an insect repellant composition comprising, consisting essentially of, or consisting of, based upon the total weight of the composition:
a. from about 6 to about 30 percent of insect repellant active material, said active material containing a functionality selected from ester, amide, urethane or combinations thereof;
b. from about 5 to about 30 percent of alcohol selected from
i. ethanol;
ii. isopropanol;
iii. a glycol monoalkyl ether, said alkyl having from about 1 carbon atom to about 4 carbon atoms;
iv. a glycol containing from about 3 carbon atoms to about 6 carbon atoms;
v. oligomers of ethylene glycol or propylene glycol; or
vi. mixtures thereof; and
c. from about 1 to about 10 percent by weight of surfactant.
The compositions and methods of this invention provide a unique means for repelling insects with a reduced rate of degradation of the active material but without disadvantageously over-drying or over-irritating the skin.